The Denver-based airline announced Tuesday that service will begin from Dulles in August and September.

Round-trip promotional fares of $30 sold out quickly. Frontier says other introductory rates will be available through Saturday.

Other cities adding service to Dulles include Atlanta, Orlando, Minneapolis, Chicago (O’Hare), Detroit, and St Louis.

Last month, Frontier announced a new fare structure that pushes it further toward the model of ultra-low-cost carriers that charge deeply discounted base fares, with additional fees for items like use of overhead bins, or extra leg room.

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